Obtaining valid consent for the collection and storage of biospecimens and data for future, unspecified research use remains a significant challenge. Numerous studies have documented that research participants in a variety of settings-including biobanking-do not understand important aspects of the research to which they consented. To correct this problem, two major challenges must be overcome. First, there is no consensus on what constitutes 'adequate' understanding in biobanking consent, creating uncertainty about when valid consent has been obtained and hampering efforts to devise and assess interventions to improve comprehension. Second, the overall quality of the evidence concerning the effects of interventions to enhance comprehension is poor. Prior studies have suffered from small sample sizes, non-randomized designs, limitations related to the characteristics of the study population, questions about how 'comprehension' was defined and measured, and a narrow focus on only selected elements of the consent process. Given the ubiquity of biobanking research, there is a critical need to overcome these challenges by defining the threshold of knowledge needed to provide truly informed consent, and developing and rigorously studying interventions to promote comprehension in the context of a complete informed consent process. Our objective for this application is to develop and assess an informed consent process for biobanking that involves a simplified consent form and an interactive test/feedback procedure to enhance comprehension. To achieve this objective, we will pursue the following aims: (1) Systematically determine the threshold of knowledge needed to demonstrate adequate biobanking consent comprehension; (2) Refine a teach-back tool to improve comprehension during the biobanking consent process; (3) Conduct a national, multisite, randomized trial to determine the individual and combined effects of a teach-back intervention and a simplified consent form on comprehension in biobanking consent; (4) Explore the individual and combined effects of a teach-back intervention and a simplified consent form on secondary consent process outcomes. The expected outcomes include a systematically-developed definition of 'adequate' understanding and high quality data demonstrating the effect of improvements to forms and processes on biobanking consent comprehension, as well as model consent forms, teach-back tools, and measures that could be readily adapted for use in any biobanking context.